Specific development features of secondary gold mineralization in mature tailings of gold processing plants

Abstract

The paper studies the development of secondary gold mineralization driven by the interaction of gold-bearing solutions with primary minerals in sulfide and oxidized ore processing tailings, as well as with secondary limonite formed during their long-term storage. Lowtemperature gas adsorption was used to establish that such tailings are characterized by high specific surface areas of up to 20 m2/g. Material surface area may play an important role in the processes of sorption and reduction. Using X-ray photoelectron spectroscopy, it has been established that secondary mineralization gold predominantly occurs in its elemental form, with a subordinate amount of the occluded ionic form of Au(I). It has been shown that Au(III) ions selectively precipitate from solutions at 25 °C and pH 6.9–7.3 on pyrite, arsenopyrite, and limonite, forming individual metal particles of 30–1000 nm, as well as mineral aggregates of complex structure and composition, including oxidized antimony minerals, limonite, and nanodispersed gold. Gold precipitation on a mixture of hydrates of iron and manganese oxides was found in samples of oxidized ore processing tailings. The specific morphology and grain-size distribution of secondary gold particles on various carrier minerals and the composition of new formations have been studied. On the secondary limonite, containing calcite (up to 10 wt%) and quartz impurities, the gold particles are up to 500 nm and are uniformly distributed over the entire material surface. This is in contrast to the sulfide and oxidized ore processing tailings, where gold was selectively reduced on certain minerals. The paper considers the potential mechanisms of gold reduction on the surfaces of oxidized minerals.The work patially was carried out within the framework of the state assignment of the Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (project No. 0287-2021-0014) using the equipment of the Federal Research Center «Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences».